MXPA97003272A - Process for developing conpropylene reticulated copolymers using a re initiator system - Google Patents

Abstract

The present invention relates to a graft copolymer of a propylene polymer material is prepared by (1) obtaining a propylene polymer material oxidized by (a) irradiating a particulate and porous propylene polymer material in the substantial absence of the oxygen, (b) exposing the irradiated propylene polymer material to a controlled amount of oxygen greater than 0.004%, but less than 15% by volume, at a temperature of 40øa 110øC, and (c) heating the irradiated polymer material to a temperature of at least 110 ° C, in the presence of a controlled amount of oxygen, within the same range as that used in the previous step, (2) dispersing the material of the oxidized propylene polymer at a temperature of 30 ° C 90 ° C, (3) adding (a) a primary reducing agent, (b) a chelating agent and (c) a secondary reducing agent, (4) adding at least one vinyl monomer and (5) recovering the graft copolymer from the reaction mixture. i

Description

PROCESS FOR DEVELOPING RETICULATED COPOLYMERS WITH PROPYLENE, USING A RÉDOX INITIATOR SYSTEM This invention relates to a method for obtaining graft copolymers of a propylene polymer material, which uses a redox initiation system. The graft copolymers of propylene polymer materials have been of interest for some time, because they exhibit some properties of one or more polymerized, grafted monomers, as well as those of the propylene polymer backbone. The graft copolymers of propylene polymer materials have been obtained by forming active sites on the backbone of the propylene polymer by treatment with peroxides or with high energy ionizing radiation, in the presence of at least one monomer capable of grafting on the sites active or followed by treatment with at least one such monomer. The free radicals produced in the propylene polymer as a result of the treatment of the irradiation or of peroxide, act as initiators for the polymerization of one or more monomers, as well as as active sites for the grafting. High-temperature vinyl monomer grafting on polypropylene, using free radical initiators, such as peroxides, results in only moderate graft efficiency (25 to 30%). HE they obtain greater efficiencies of the graft when free radicals are produced by irradiation instead of with peroxides. However, when conventional, low porosity propylene polymer particles are used, the grafting takes place primarily at the surface of the particles and, therefore, the distribution of the polymerized graft monomer is not uniform throughout the particles of the graft. polymer. "Redox" polymerization systems, which contain both oxidizing and reducing agents, have been used to produce graft copolymers. Free radicals are generated at considerably lower temperatures than when peroxides are used to generate these free radicals. Organic peroxides are typically used as the oxidizing agent and ferrous ions as the reducing agent. The colloidal dispersions can be used, from which sufficient ferrous ions are released through the polymerization, to react with the hydroperoxide and peroxide groups that are formed in the polymer. Secondary reducing agents, such as sugars and sodium formaldehyde sulfoxylate, are often used to ensure the presence of the ferrous ions for the improved efficiency of the initiation and the constant rate of polymerization throughout the course of the reaction.

The application of the redox systems to the emulsion polymerization has led to a significant improvement in several commercial processes, such as the manufacture of styrene / butadiene rubber latex. The use of redox systems is also applicable to heterogeneous systems, where oxidizing and reducing agents are not miscible. Emulsion polymerization is generally used in such cases. For example, polypropylene can be grafted with water insoluble monomers using water insoluble polypropylene peroxides as the oxidizing agent in an aqueous emulsion, in the presence of ferrous salts as the reducing agent and a surfactant. The decomposition of such polypropylene peroxides generates polypropylene oxide radicals which are capable of initiating the polymerization of several monomers, even at low temperatures. The effect of several metal ions, in the presence of a chelating agent, triethylene tetraamine (TETA) on the graft of the isotactic polypropylene oxidized with the styrene in emulsion, was evaluated at 352C by Mikulasova et al., In Chem. Zvesti, 27, 263-267 (1973). The ability of iron (II) sulfate to activate the grafting of vinyl and diene monomers in polypropylene, in the presence of various chelating agents, was investigated by Citovicky et al., Chem. Zvesti. 27 f 268-272 (1973). In both of these systems, a non-porous isotactic powder polypropylene was oxidized by oxygen with an ozone concentration of 12 mg / 1 at room temperature (~ 25dC). A process for hydroperoxidation of a polymer by the contact of an aqueous suspension of a polymer having hydrogen bonded to tertiary carbon atoms in the polymer chain, with molecular oxygen, in the presence of a surface active cationic agent is revealed in USP 3,458,597. The graft copolymers can be prepared by contacting the hydroperoxidized polymer with a vinylidene monomer, in the presence of a redox reducing agent, at 90 ° C. The process of this invention for obtaining a graft copolymer of a propylene polymer material comprises: (1) obtaining a propylene polymer material oxidized by (a) irradiating a particulate polypropylene material, having (i) a fraction of pore volume of at least 0.07, in which more than 40% of the pores have a diameter greater than 1 miera, (ii) a surface area of at least 0.1 m2 / g, and (iii) an average diameter of approximately 0.4 a 7 mm, in an environment in which the active oxygen concentration is equal to or less than 0.004% by volume, (b) exposing the irradiated propylene polymer material to a controlled amount of oxygen of more than 0.004% and less than 15%. % in volume, at a temperature from about 40 to 11O ^ c, and (c) heating the irradiated polymer to a temperature of at least 110se, in the presence of a controlled amount of oxygen, within the same range as that used in (b), (2) dispersing the resulting oxidized propylene polymer material in water, in the presence of a surfactant, at a temperature of about 30 to 90 ° C, (3) adding (a) a primary reducing agent, (b) a chelating agent and (c) ) a secondary reducing agent, (4) adding at least one vinyl monomer and (5) recovering the graft copolymer from the reaction mixture. The reaction temperature and the porous nature of the polymeric starting material used in the process of this invention, shortens the reaction time of the graft polymerization, improves the conversion of the graft monomer to the polymer (both grafted and non-grafted polymers), improves the efficiency of the graft, gives better control of the weight-average molecular weight (Mw of the ungrafted polymer present in the particles and provides a more uniform distribution of the graft monomer polymerized in the matrix of the propylene polymer material. a photomicrograph 47X of a microtomy contrasted in phase, of a cross-section of a particle of high porosity of the grafted polypropylene with styrene, in which the polymerized styrene was uniformly dispersed within the particle. The area and direction of the mapping path is displayed. Figure 2 is a projection of the polystyrene content at a specific point against the corresponding distance in microns from the edge of the particle shown in Figure 1. The data was collected by infrared spectroscopy. Figure 3 is a 50X photomicrograph of a microtomy contrasted in phase, of a cross section of a low porosity particle of polypropylene grafted with styrene, in which the polymerized styrene was concentrated around the surface of the particle. Figure 4 is a projection of the polystyrene content at a specific point against the corresponding distance in microns, from the edge of the particle shown in Figure 3. The data was collected by infrared spectroscopy. The area and direction of the mapping path are displayed. The propylene polymer material used as the starting material in the process of this invention is (a) a propylene homopolymer, (b) a random copolymer of propylene with ethylene or an alpha-olefin, linear or branched, with 4 to 10 carbon atoms, with the proviso that when the comonomer is ethylene, the content of Maximum polymerized ethylene is 10%, preferably about 4%, and when the comonomer is an alpha-olefin with 4 to 10 carbon atoms, its maximum polymerized content is 20%, preferably 16% or (c) a terpolymer of propylene and two different alpha-olefins selected from the group consisting of ethylene and alpha-olefins with 4 to 8 carbon atoms, with the proviso that when ethylene is one of the different alpha-olefins, the polymerized ethylene content maximum is 5%, preferably 4%, and when the different alpha-olefin is an alpha-olefin of 4 to 8 carbon atoms, the maximum polymerized content of the alpha-olefin of 4 to 8 carbon atoms is 20%, preferably around 16%. The alpha-olefins with 4 to 10 carbon atoms that can be used when the propylene polymer material is a random copolymer or a terpolymer of propylene, include, for example, l-butene, isobutylene, 3 ^ methyl-l- butene, 3,4-dimethyl-1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 3-methyl-1-hexene, 1-heptene, 1-octene and 1-decene. The propylene polymer material has (a) a pore volume fraction of at least 0.07, where no more than 40% of the pores have a diameter greater than 1 miera, (b) a surface area of at least 0.1 m2 / g, and (c) an average diameter of approximately 0.4 to 7 mm. The use of porous polymer particles, as opposed to the small diameter of conventional pores, low porosity or non-porous particles of the propylene polymer material improves the uniformity of the polymerized monomer distribution within the matrix of the propylene polymer material, improves the grafting efficiency and improves the molecular weight control of the non-polymer grafted. Low porosity and non-porous polymer materials tend to oxidize only the surface of the particles and, therefore, do not have a uniform distribution of the polymerized monomer through the particle; rather, they form shell / core type particles with the propylene polymer that forms the core and the grafted polymer of the shell. The starting material of the propylene polymer is exposed to high energy ionizing radiation in an environment essentially free of oxygen, ie an environment in which the concentration of active oxygen is established and maintained at 0.004% by volume or less. Ionizing radiation is established and maintained at 0.004 $ in volume or less. This ionizing radiation must have sufficient energy to penetrate the desired extent in the mass of the propylene polymer material that is irradiated. Ionizing radiation can be of any kind, but the most practical classes are electrons or qamma rays. Electron beams are preferred from a generator thereof, which have an acceleration potential of 500 to 4,000 kilovolts. Satisfactory results are obtained at a dose of ionizing radiation of approximately 0.5 to 15 mega-rads, preferably around 0.5 to 10 mega-rads. The term "rad" is usually defined as the amount of ionizing radiation that results in the absorption of 100 ergs of energy per gram of irradiated material. The energy absorption of the ionizing radiation is measured by the well-known conventional dosimeter, a measuring device in which a strip of the polymer film containing a radiation-sensitive dye is the means of detecting the absorption of energy. Therefore, as used in this specification, the term "rad" means that the amount of ionization radiation resulting in the absorption of the equivalent of 100 ergs of energy per gram of the polymer film of a dosimeter, placed in the surface of the irradiated propylene polymer material, which is in the form of a bed, a particle layer or a film or a sheet. The irradiated propylene polymer material, which contains the free radical, is then subjected to a series of oxidative treatment steps. The preferred way to carry out the treatment is to pass the irradiated polymer through a first fluid bed assembly, which operates at Tl in the presence of a controlled amount of oxygen, and then through a second fluid bed assembly, operating at 2, in the presence of a controlled amount of oxygen, within the same interval as in the first stage. In commercial operation, a continuous process using separate fluid beds is preferred. However, the process can also be carried out in a batch mode in a fluid bed, using a stream of fluidization gas heated to the desired temperature for each treatment step. Unlike some techniques, such methods of extrusion of the melt, the fluidized bed method does not require the conversion of the irradiated polymer into the molten state and the subsequent resolidification and grinding in the desired form. The first stage of treatment consists in heating the polymer in the presence of a controlled amount of active oxygen, in a range greater than 0.004%, but less than 15% by volume, preferably less than 8% and more preferably less than 3%, at a temperature of about 40 to about HO ^ C, preferably about 802C. Heating to the desired temperature is achieved as quickly as possible, preferably in less than 10 minutes. The polymer is then maintained at the selected temperature, typically for about 90 minutes, to increase the rate of reaction of the oxygen with the free radicals in the polymer. The retention time, which can be easily determined by a person skilled in the art, depends on the properties of the starting material, the concentration of the oxygen used, the irradiation dose and the temperature. The maximum time is determined by the physical limitations of the fluid bed. In the second stage of treatment, the polymer is heated in the presence of a controlled amount of oxygen, in the same range used in the first treatment step, at a temperature of at least lióse up to the softening point of the polymer (1402C for the propylene homopolymer). The polymer is then maintained at the selected temperature, typically for about 90 minutes, to increase the rate of chain cleavage. The retention time is determined by the same factors discussed in relation to the first stage of treatment. The polymer is then cooled to a temperature of about 70 ° C over a period of about 10 minutes in an atmosphere essentially free of oxygen, ie 0.004% by volume or less, before being discharged to the bed. In this way, stable intermediate products are formed which can be stored at room temperature for extended periods of time without further degradation. The term "active oxygen" means oxygen in a form that reacts with the irradiated propylene polymer material. It includes molecular oxygen, which it is in the form of the oxygen normally found in the air. The active oxygen content requirement of the process of this invention can be achieved by the use of a vacuum or by replacing part or all of the air in the environment with an inert gas, such as, for example, nitrogen or argon. The concentration of the peroxide groups, formed in the polymer, can be easily controlled by varying the radiation dose and the amount of oxygen to which the polymer is exposed after irradiation. The level of oxygen in the fluid bed gas stream is controlled by the addition of air at the inlet of the fluid bed. The air will be added constantly to compensate for the oxygen consumed by the formation of peroxides in the polymer. The fluidization medium can be, for example, nitrogen or any other gas which is inert with respect to the free radicals present, for example argon, krypton and helium. The material of the oxidized propylene polymer is then dispersed in water, in the presence of a surfactant, at a temperature of about 30 ° C to about 90 ° C, preferably about 65 ° C to about 80 ° C. The surfactants used in the process of the invention can be anionic, cationic or non-ionic, depending on the miscibility with water of the one or more monomers used for the graft. For example, sodium myristate, an anionic surfactant, is preferred for the polymerization of styrene and a polyoxyethylene ether of a long chain alkanol, a nonionic surfactant is preferred for methyl methacrylate. The formation of an aqueous paste of the oxidized propylene polymer material, before the addition of the reducing agents, produces better diffusion of the reducing agents in the matrix, in order to react with the peroxy groups in the polymer and generate free radicals . The surfactant also forms an emulsion with the monomer immiscible with water and forms stable micelles, as well as improving the solubility of the monomer in the aqueous phase. Approximately 0.1 to 1.0% of the surfactant, based on the amount of water, is typically used. Suitable anionic surfactants include, for example (a) alkali metal salts of organic carboxylic acids, having the general formula RC00-M +, where R is a long-chain hydrocarbon group (C9-C22) and M is a metal ion or ammonium; (b) alkali metal salts of sulfonates, of the general formula R-SO3-M +, where R is an alkyl, aryl or alkylaryl group, linear or branched, and m is a metal ion, and (c) alkali metal salts of long chain fatty acid sulfates, which have the formula RS? ~ M ++, where R is an alkyl group, linear or branched, from 9 to 22 carbon atoms, and M is a metal ion. Suitable cationic surfactants include, for example, monoamines or primary, secondary and tertiary diamines and their quaternary ammonium salts, R-N + R'R "RI", and substituted, long-chain cyclic amine salts having the formula R-N +, such as pi - »-" > dina, morpholine and piperidine, where R is a linear or branched alkyl or alkenyl group, of 1 to 18 carbon atoms, and R ', R "and R1" are H or R. Other examples of cationic surfactants include chloride of cetyltrimethylammonium, distearyl dimethyl ammonium chloride, n-hexadecyltrimethyl-onium bromide and n-decyltrimethylammonium bromide. Suitable nonionic surfactants include, for example, esters of polyalcohols and long chain fatty acids, having the formula RCOO- [CH 2 CH 20] n H, where n is 4-20 and R is a linear or branched alkyl group of 9 to 21 carbon atoms, polyoxyethylene ethers of long chain alkanols, having the formula RO - [- CH2CH2? -] nH, where R is an alkyl group, linear or branched, of 9 to 21 carbon atoms and n is 4-23, and ethoxylated alkylphenol homologs of the general formula R-Ar-0- [CH CH 2?] N -CH 2 CH 2? H, where R is an alkyl group, linear or branched, Ar is an aryl group and n is 2- 40 The following components are then added to the aqueous emulsion of the oxidized polymer: (1) a primary reducing agent, (2) a chelating agent and (c) a secondary reducing agent. Suitable reducing agents for use in the process of this invention include the salts of the inorganic acid transition metals, for example the sulfates and nitrates. Metals having more than one oxidation state, selected from Groups IB (for example, Cu, Ag), IIIB (for example, Ce), IVB (for example Ti), VB (for example V), VIB (for example example, Cr, Mo), VIIB (Mn) and VIIIB (Fe, Co, Ni), from the Periodic table, are normally used. Ferrous sulfate is preferred. The reducing agent is preferably used in a molar ratio of oxygen, in the oxidized polymer, to the reducing agent, of about 1: 1. Chelating agents suitable for use in the process of this invention contain two or more electron donor atoms which can form coordinated bonds to a single transition metal atom, which creates a ring structure containing a metal ion. Examples include ethylenediaminetetraacetic acid, hydroxyethylenediaminetriacetic acid, nitrilotriacetic acid, citric acid, tartaric acid, gluconic acid, 5-sulfosalicylic acid, ethylenediamine, diethylene triamine, triethylene tetraamine, triaminotriethylamine, triethanolamine, N-hydroxy ethylenediamine and sodium oxalate. Triethylene tetraamine is preferred. The concentrations of the reducing and chelating agents depend on the concentration of oxygen in the oxidized propylene polymer material and typically are in the range of 0.05 to 1 equivalent of the reducing agent or the chelating agent per equivalent of oxygen in the oxidized polymer . The molar ratio of the chelating agent to the reducing agent is typically in the range of 2: 3 to 1: 1. Secondary reducing agents are used to ensure a constant concentration of the reducing metal ions throughout the polymerization period, thus ensuring an efficient polymerization start and a constant polymerization rate. Suitable examples of secondary reducing agents include sugars, such as fructose and glucose, dihydroxyacetone and sodium formaldehyde sulfoxylate (SFS). Suitable monomers for the backbone graft of the propylene polymer material can be any monomeric vinyl compound, in which the vinyl radical, CH2 = CR-, wherein R is H or methyl, is attached to an aliphatic, straight chain or branched, or an aromatic, heterocyclic or alicyclic ring, substituted or unsubstituted, in a mono- or polycyclic compound. Substituent groups typical may be alkyl, hydroxyalkyl, aryl and halogen. Usually, the vinyl monomer will be a member of one of the following classes: (1) vinyl-substituted aromatic, heterocyclic or alicyclic compounds, including styrene, vinylnaphthalene, vinylpyridine, vinylpyrrolidone, vinylcarbazole, methylstyrenes, methylchlorostyrene, p-tert. -butylstyrene, methylvinylpyridine and ethylvinylpyridine, and (2) (meth) acrylic nitriles and (meth) acrylic acid esters, such as acrylonitrile, methacrylonitrile, acrylate esters, such as methyl, ethyl, hydroxyethyl acrylate esters, -ethylhexyl and butyl, and methacrylate esters, such as methacrylate esters of methyl, ethyl, butyl, benzyl, phenylethyl, phenoxyethyl, epoxypropyl and hydroxypropyl. Of the various vinyl monomers that can be used, styrene, acrylonitrile, butyl acrylate, 2-ethylhexyl acrylate, methyl acrylate, methyl methacrylate, butyl methacrylate, and mixtures thereof are preferred. The graft monomer is added to the emulsion after the reagents previously added have had time to diffuse into the porous material of the propylene polymer, typically after 10-12 minutes. A maximum of 120 parts of the graft monomer per hundred parts of the oxidized polymer is preferred.

During graft polymerization, the one or more monomers also polymerize or copolymerize to form a certain amount of free or ungrafted polymer or copolymer. The morphology of the grafted polymer is such that the propylene polymer material is continuous phase or matrix and the one or more polymerized monomers, both grafted and ungrafted, are in a dispersed phase. A grafting efficiency of more than 60% is preferred. At the end of the graft polymerization reaction, the graft copolymer is recovered from the reaction mixture, for example by washing with excess water and then ethanol-HCl, and then drying. The miro-structural differences between the grafted propylene homopolymer material of this invention and the grafted propylene homopolymer material obtained by the graft polymerization on a conventional low porosity small porosity propylene homopolymer can be seen with reference to Figures 1 to 4. In Figure 1, which shows a particle of the grafted propylene homopolymer of the invention, ie particles of the product described in Example 7, the regions of the high concentration of the polystyrene, i.e. a grafted polystyrene to the propylene homopolymer, they are seen not only on the surface of the particle but through and deep into the interior of the particle. The presence of polystyrene in these regions were confirmed by means of the infrared scanning microscope of the Fourier transformation, as shown in Figure 2. In a product particle prepared from a commercially available low porosity polypropylene, shown in Figure 3, the high level The polystyrene is essentially confined to regions around the outer surface of the particle. The content of the styrene inside this particle, if any, is extremely low, indicating an essentially ungrafted propylene homopolymer core. This was confirmed by the IR scanning microscopy, as shown in Figure 4, ie the scanning microscope did not show any polystyrene content inside this particle. In the following examples, the flow rate of the melt ("MFR") of the oxidized polypropylene was determined by ASTM D-1218, Condition L (230se, 2.16 kg (and the MFR of the product was determined by the standard ASTM D-1238, at 2302C, using a weight of 3.8 kg The efficiency of grafting is defined as the weight% of the grafted polymer, actually grafted onto the propylene polymer material, calculated from the measurement of soluble substances. in xylene.% of substances soluble in xylene, at 252C, was determined by dissolving 2 g of the polymer in 200 ml of xylene at 135 ° C, cooling in a constant temperature bath to 252 ° C and filtering through fast filtration paper.

An aliquot of the filtrate was evaporated to dryness, the residue was weighed and the weight% of the soluble fraction was calculated. The molecular weights of the soluble fraction were determined by gel permeation chromatography, using the Perkin Elmer isocratic LC pump 250 and a refractive index or UV detector at 260 nm. Unless otherwise specified, all parts and percentages in this specification are by weight. EXAMPLE 1 This example illustrates how the polymerization of styrene is affected during the preparation of the styrene-grafted polypropylene by the grafting reaction temperature. A propylene homopolymer was irradiated by the process described above, with a radiation dose of 2 Mrad. The irradiated polymer was exposed to 1000 ppc (0.1% by volume) of active oxygen in the first and second stages of treatment. The oxidized polymer, therefore, had an oxygen concentration of 1000 ppm. In the first treatment step, the polymer was heated to 802C and maintained at that temperature for 90 minutes. In the second treatment step, the polymer was heated to 140 ° C and held at that temperature for 60 minutes. The propylene homopolymer had a surface area of 0.3 m2 / g, an average diameter of 1.9 mm, a fraction of the pore volume of 0. 31, where more than 90% of the pores had a diameter greater than 1 miera, a porosity of 0.47 cc / g, an MFR of 23 dg / min and a weight-average molecular weight (Mw) of 230,000, and is available from Montell USA Inc. Reaction Temperature of 35 ^ 0 A stirred suspension of oxidized polypropylene (100 g, 3.12 mmol) and sodium myristate (0.68 g, 0.15%) in deionized water (460 ml) (water / monomer = 5.5), purged with nitrogen and heated to 353C. After 20 minutes at 352C, FeS? 4 (0.8 g, 2.88 mmol), triethylenetetraamine (TETA) (0.64 g, 4.4 mmol) and glucose (1.0 g, 5.56 mmol) were added. After 15 minutes, styrene (85 g, 85 parts of styrene per hundred parts of the oxidized polymer (ppc) was added slowly.The reaction mixture was stirred with a mechanical stirrer for six hours at 35 ° C and left at room temperature for 15 hours (overnight) The suspended polymer was filtered on a Buchner funnel and washed with excess water and methanol (200 ml) The product was soaked in methanol (500 ml) for several hours and filtered again The polymer was then dried in a vacuum oven at 80-lOOsc Reaction Temperature of 50 ° C A stirred suspension of oxidized polypropylene (50 g, 1.56 mmol) and sodium myristate (0.34 g, 0.15%) in deionized water ( 230 ml) was purged with nitrogen and heated to 50 ° C. The FeS 4 (0.4 g, 1.44 mmol) was added at 50 ° C.

TETA (0.32 g, 2.2 mmol) and glucose (0.5 g, 2.78 mmol). After 15 minutes, styrene was added slowly (42.5 g, 85 ppc). The reaction mixture was stirred for three hours at 50 seconds. The product was isolated as described above. Reaction Temperature of 6Q2C A stirred suspension of oxidized polypropylene and sodium myristate in deionized water in the amounts given above was purged with nitrogen and heated to 60 ° C. FeS04, TETA and glucose were added at 502C in the amounts given above. The reaction mixture was stirred with a mechanical stirrer for three hours at 60 ° C. The product was isolated as described above. Reaction temperature of 7Q2C A stirred suspension of oxidized polypropylene and sodium myristate in deionized water, in the amounts given above, was purged with nitrogen and heated to 702C. The FeS04, TETA and glucose were added at 602C in the amounts given above and in the order given. After 15 minutes, the styrene, in the given amount, was slowly added to 70se. The reaction mixture was stirred with a mechanical stirrer for three hours, at 70 ° C. The product was isolated as described above. Reaction Temperature of 8Q2C A stirred suspension of oxidized polypropylene and sodium myristate in deionized water, in the amounts given above, it was purged with nitrogen and heated to 802C. The FeS0, TETA and glucose were added at 70 C in the amounts given above and in the order given. After 10 minutes, the styrene, in the given amount, was slowly added at 80 ° C. The polymer was free flowing in 30 minutes, indicating completion of the reaction. After stirring for a further two hours at 80 ° C, the product was isolated as described above. For each reaction temperature, the% conversion of styrene monomer to polystyrene (both grafted and ungrafted), the MFR of the product, the Mw and Mw / Mn of the grafted polystyrene, and the efficiency of the graft ("GE"), are given in Table 1. Table l EXAMPLE 2 This example illustrates how the polymerization of styrene is affected during the preparation of the styrene-grafted polypropylene by the dose of radiation absorbed during irradiation of the propylene homopolymer. A propylene homopolymer (PP), described in Example 1, was irradiated as described in Example 1, using absorbed radiation doses of 0.5, 2 and 6 Mrad. In each case, the polymer was exposed to an oxygen concentration of 1000 ppm (0.1% by volume). A stirred suspension of each sample of oxidized polypropylene (50 g) and sodium myristate (0.34 g, 0.15%) in deionized water (230 ml) was purged with nitrogen and heated to 50 ° C. The suspension, at 502C, was added to the FeS04 (0.4 g, 1.44 mmoles), TETA (0.32 g, 2.2 mmoles) and glucose (0.5 g, 2.78 mmoles). After 10 minutes, styrene (42.5 g, 85 ppc) (water / monomer = 5.5) was slowly added. The reaction mixture was stirred with a mechanical stirrer for three hours at 50 ° C. The product was isolated as described in Example 1. The% conversion of styrene monomer to polystyrene (both grafted and ungrafted) the MFR of the product, the weight average molecular weight Mw and the molecular weight distribution (Mw / Mn) ) of the Non-grafted polystyrene, and graft efficiency (GE) for such radiation dose, are given in Table 2. Table 2 The data show that the efficiency of graft formation increased with the increasing radiation dose. Example 3 This example illustrates how polymerization of styrene affects the preparation of styrene-grafted polypropylene by the concentration of oxygen to which the propylene homopolymer was exposed after irradiation. Oxidized polypropylene samples were prepared by exposing the propylene homopolymer to 1000, 3000 and 20,000 ppm of oxygen (0.1, 0.3 and 2.0% by volume), after the irradiation process described in Example 1. The propylene homopolymer used for the first two experiments was the same as that used in Example 1. The propylene homopolymer exposed to 20, 000 ppm of oxygen was not porous (porosity of 0.15 cc / g), had an MFE of 0.8 dg / min and an Mw of 800,000 and is available from Montell USA Inc. Each of the oxidized polypropylene samples (100 g) was suspended in deionized water (460 ml) containing 0.68 g (0.15%) of sodium myristate and the suspension was purged with nitrogen and heated to 35 C. After 20 minutes at 352C, FeS04 (0.8 g, 2.88 mmole), TETA (0.64 g, 4.4 mmol) and glucose (1.0 g, 5.56 mmol). After 15 minutes, styrene was added slowly (85g, 85 ppc). The reaction mixture was stirred with a mechanical stirrer for six hours at 352C and left at room temperature for 15 hours (overnight). The product was isolated as described in Example 1. The% conversion of styrene monomer to polystyrene (both grafted and ungrafted), the product MFR, the Mw and the Mw / Mn of ungrafted polystyrene, and the efficiency of graft formation are given in Table 3.

Table 3 The% conversion and the grafting efficiency increased and the Mw of the ungrafted polystyrene decreased with an increase in the concentration of oxygen to which the polymer was exposed after irradiation. Example 4 This example describes how the polymerization of styrene affects the preparation of styrene-grafted polypropylene by the use of various reducing agents. All reactions were carried out as described under "802C Reaction Temperature" in Example 1, using oxidized polypropylene (6 Mrad, 1000 ppm of O2), sodium myristate as the surfactant, TETA as the chelating agent and glucose as the secondary reducing agent. The% conversion of the styrene monomer to the polystyrene (both grafted and ungrafted), the product MFR, the Mw and the Mw / Mn of the ungrafted polystyrene, and the efficiency of grafting are given in Table 4. Table 4 Ferrous sulfate provided high values for both the% conversion and the efficiency of grafting.

Example 5 This example describes how the molar ratio of the oxygen in the oxidized polymer to the reducing agent affects the polymerization of the styrene during the preparation of the styrene-grafted polypropylene. All reactions were carried out as described in Example 1, using oxidized polypropylene (2 Mrad, 1000 ppm 02, MFR 770) (300 g, 9.4 mmol 02) and sodium myristate as the surfactant . FeS04 (2.43 g, 8.7 mmol), TETA (1.89 g, 13 mmol) and glucose (3.0 g, 16.7 mmol) were added at 55 C and styrene (255 g, 85 ppc) was added at 65 SC, after 10 minutes. The ratio of oxygen, in the oxidized polymer, to the reducing agent was approximately 1: 1. The product was isolated as described in Example 1. The same experiment was repeated, except that 0.59 g of FeS04 (2.12 mmol), 0.47 g of TETA (3.2 mmol) and 0.76 g of glucose (4.22 mmol) were added. The ratio of oxygen, in the oxidized polymer, to the reducing agent was approximately 4: 1. The% conversion of the styrene monomer to polystyrene (both grafted and ungrafted), the product MFR, the Mw and the Mw / Mn of the ungrafted polystyrene, and the efficiency of the graft formation are given in Table 5.

Table 5 The% conversion and grafting efficiency decreased and the Mw of the ungrafted polystyrene increased when the molar ratio of the oxygen concentration, in the oxidized polymer to the reducing agent, increased from 1: 1 to 4: 1. Example 6 This example describes how the polymerization of styrene affects the preparation of styrene-grafted polypropylene by the use of various chelating agents.

All reactions were carried out as described under "802f Reaction Temperature" in Example 1, using oxidized polypropylene (6 Mrad, 1000 ppm O2), sodium myristate as the surfactant, FeS04 as the agent primary reducer and glucose as the secondary reducing agent. The% conversion of styrene monomer to polystyrene (both grafted and ungrafted), product MFR, Mw, Mw / Mn of ungrafted polystyrene and grafting efficiency are given in Table 6. In the Table, TETA is triethylene tetraamide, ED is ethylenediamine, EDTA Na4 is the tetrasodium salt of ethylenediaminetetraacetic acid, NTA Na3 is the trisodium salt of nitriloacetic acid, and EDTA is ethylenaminotetraacetic acid. The ratio of the reducing agent to the chelating agent was 1.4 / 4.3 for the ED. In all other cases, the ratio was 1: 1.

Table 6 The use of TETA as a chelating agent, in combination with FeS04 as a reducing agent, produced the highest values for% conversion and grafting efficiency. Example 7 This example illustrates how the porosity of the polypropylene, which is irradiated, and the grafting reaction temperature, affect the dispersion of the polystyrene in the polypropylene matrix. The oxidized polypropylene that was exposed to 20,000 ppm of oxygen, used in Example 3 (low porosity, O2 concentration of 20,000 ppm, grafting temperature of 352C) differs from the oxidized polypropylene of Example 5 (high porosity, 02 concentration of 1000 ppm, grafting temperature of 652C). In order to compare the uniformity of the polystyrene dispersion in the polypropylene matrix, IR spectrum of microtomy sections of 10-15 microns of spheres were recorded under computer control every 6 microns across the length of the sphere . The level of the polystyrene calculated at each point was projected against the corresponding distance in microns from the edge of the sphere (0-200 ppc of polystyrene). This polystyrene is more evenly dispersed in graft polymers obtained from the porous oxidized polypropylene (Example 5), as shown in Figures 1 and 2. In the particles obtained from the low porosity oxidized polypropylene (Example 3), in spite of having At times more reaction sites, the polystyrene was concentrated on the surface of the sphere and there was very little in the matrix (Figures 3 and 4). Example 8 This example describes the preparation of polypropylene grafted with methyl methacrylate (MMA) using various surfactants, FeS04 as the reducing agent, TETA as the chelating agent and glucose as the secondary reducing agent.

The propylene homopolymer, described in Example 1 was irradiated according to the process described in this Example 1. The absorbed radiation dose was 6 Mrad and the polymer was exposed to 1000 ppm 02 (0.1% by volume) after irradiation. All reactions were carried out as described under "802C Reaction Temperature" in Example 1. The amount of oxidized polymer used was 50 g. The surfactant was added at 50-552C (0.53 g, 0.23%). FeS0 (0.4 g, 1.44 mmol), TETA (0.32 g, 2.2 mmol) and glucose (0.5 g, 2.8 mmol) were added to 70SC. The MMA was added to 80SC after 10-12 minutes, and the reaction mixture was stirred for three hours. The product was recovered as described in Example 1.% conversion of MMA monomer to poly (MMA) (both grafted and ungrafted), the MFR of the product, 1 Mw and the Mw / Mn of the poly (MMA) without grafting and grafting efficiency, are given in Table 7.

Table 7 The use of Brij 35 nonionic surfactant provided the highest values for% conversion and grafting efficiency. EXAMPLE 9 This example describes the preparation of the polypropylene grafted with styrene and the methyl methacrylate monomers. The propylene homopolymer, described in Example 10, was irradiated as described in Example 1, using a dose of absorbed radiation of 0.5 Mrad, and the The irradiated polymer was exposed to an oxygen concentration of 2000 ppm (0.2% by volume) after irradiation. The grafting reaction was carried out as described in Example 1, using 50 g of oxidized polypropylene (3.12 mmole of O2) and 0.57 g of sodium myristate (0.25%) as the surfactant at 352C. FeS04 (0.8 g, 2.8 mmol), TETA (0.64 g, 4.4 mmol) and glucose (1.0 g, 5.5 mmol) were added to 35SC. After ten minutes, styrene and MMA (1: 1, 21.5 g each, 85 ppc in total) were added. After stirring for six hours at 352c, the reaction mixture was left at room temperature overnight. The polymer was recovered as described in Example 1. The% conversion of the monomers to the styrene / MMA copolymer (both grafted and ungrafted) was 80% (84.1 g) and the grafting efficiency was 36%. Example 10 This example illustrates the preparation of polypropylene grafted with styrene, according to the process of this invention. A propylene homopolymer was irradiated by the process described in Example 1, k at a radiation dose of 0.5 Mrad. The irradiated polymer was exposed to 0.2 volume% oxygen in the first and second treatment stages. The homopolymer of propylene had a melt flow rate (MFR) of 9 dg / in, an area surface area of 0.3 m2 / g, a pore volume fraction of 0.28, in which more than 90% of the pores had a diameter greater than 1 miera, an average diameter of 1.9 mm, a porosity of 0.45 cc / g, and a Mw of 170,000, and is available from Montell USA Inc. A stirred suspension of the oxidized polypropylene (225 g, 14.06 mmole of O2) in deionized water (883 ml) in a 2 liter glass reactor, was purged with nitrogen and the suspension it was slowly heated to 50sc. At 402C, a suspension of sodium myristate (3.1 g, 0.15%) in deionized water (50 ml) was added to the suspension. At 502c, solutions of FeS04 (1.9 g, 6.5 mmol), TETA (1.52 g, 10.4 mmol) and glucose (2.7 g, 15 mmol) in 15 ml of deionized water were added each. after 10 minutes, the styrene (191.25 g, 85 ppc) (water / monomer = 5.5) was slowly added to the reactor and the reaction mixture was stirred for five hours. This reaction mixture was cooled to room temperature and the suspended polymer was recovered as described in Example 1. The weight of the final product was 397 * 2 g. The conversion of styrene to polystyrene (both grafted and ungrafted) was 90%. Comparative Example 11 This comparative example illustrates the preparation of the styrene-grafted polypropylene by the method described in Example 10, except that no reducing agent was used.

The example demonstrates that the grafting reaction of Example 10 took place by the polymerization mechanism initiated by redox, rather than by thermal decomposition. A stirred suspension of the oxidized polypropylene, prepared as described in Example 10 (225 g, 14.06 mmol) in deionized water (1001 ml) in a two liter glass reactor, was purged with nitrogen and the suspension heated slowly to 50 ° C. . At 40BC a suspension of sodium myristate (3.1 g, 0.15%) in deionized water (50 ml) was added to the suspension. At 502C, styrene (191.25 g, 85 ppc) (water / monomer = 5.5) was slowly added to the reactor and the reaction mixture was stirred for five hours. The reaction mixture was cooled and the suspended polymer was filtered, washed and dried as described in Example 1. The weight of the final product was 242.2 g. Only 9% of the styrene was converted to the polymer. Other characteristics, advantages and embodiments of the invention described herein will be readily apparent to those of ordinary skill in the art, after reading the above description. In this regard, while specific embodiments of the invention have been described in considerable detail, variations and modifications of these embodiments can be made, without departing from the spirit and scope of the invention, as described and claimed.

Claims (13)

1. CLAIMS 1. A process for obtaining a graft copolymer of a propylene polymer material, this process comprises: (1) obtaining a propylene polymer material oxidized by (a) irradiating a particulate polypropylene material, having (i) a fraction of pore volume of at least about 0.07, in which more than 40% of the pores have a diameter greater than 1 miera, (ii) a surface area of at least 0.1 m2 / g, and (iii) an average diameter from about 0.4 to 7 mm, in an environment in which the concentration of active oxygen is equal to or less than 0.004% by volume, (b) exposing the irradiated propylene polymer material to a controlled amount of oxygen greater than 0.004% and less than 15% by volume, at a temperature of about 40 to 110 ° C, and (c) heating the irradiated polymer to a temperature e at least lyóse, in the presence of a controlled amount of oxygen, within the same range as that used in (b); (2) dispersing the resulting oxidized propylene polymer material in water, in the presence of a surfactant, at a temperature of about 30 to 90 ° C; (3) add (a) a primary reducing agent, (b) a chelating agent and (c) a secondary reducing agent; (4) add at least one vinyl monomer; Y (5) recovering the graft copolymer from the reaction mixture.
2. 2. The process of claim 1, wherein the propylene polymer material is selected from the group consisting of (a) a propylene homopolymer, (b) a random copolymer of propylene with ethylene or an alpha-olefin, linear or branched, having 4 to 10 carbon atoms, with the proviso that, when the comonomer is ethylene, the maximum content of polymerized ethylene will be 10% and, when the monomer is an alpha-olefin of 4 to 10 carbon atoms, its Maximum polymerized content will be 20%, or (c) a terpolymer of propylene and two different alpha-olefins selected from the group consisting of ethylene and alpha-olefins of 4 to 8 carbon atoms, with the proviso that, when ethylene is one of the different alpha-olefins, the maximum content of polymerized ethylene is 5%, and when the alpha-olefin other is an alpha-olefin having 4 to 8 carbon atoms, the maximum polymerized alpha-olefin with 4 to 8 carbon atoms It will be 20%.
3. 3. The process of claim 2, wherein the propylene polymer material is a propylene homopolymer.
4. 4. The process of claim 1, wherein the temperature, in step (2), is from about 65 to 80SC.
5. 5. The process of claim 1, wherein the reducing agent is a salt of an inorganic acid of a transition metal, selected from the group of metals of Group IB, IIIB, IVB, VB, VIB, VIIB and VIIIB, of the table Periodic
6. 6. The process of claim 5, wherein the reducing agent is ferrous sulfate.
7. 7. The process of claim 1 wherein the chelating agent is selected from the group consisting of ethylenediaminetetraacetic acid, hydroxyethylethylenediamine-diaminotriacético acid, nitrilotriacetic acid, citric acid, tartaric acid, gluconic acid, 5-sulfosalicylic acid, ethylenediamine, diethylenetriamine, triethylenetetramine , triamine-triethylamine, triethanolamine, N-hydroxyethylethylenediamine and sodium oxalate.
8. 8. The process of claim 7, wherein the chelating agent is triethylenetetraamine.
9. 9. The process of claim 1, wherein the vinyl monomer is a compound in which the vinyl radical CH 2 = CR, wherein R is H or a methyl group, is attached to an aliphatic, straight or branched chain, or an aromatic ring , heterocyclic or alicyclic, substituted or unsubstituted, in a mono- or polycyclic compound.
10. 10. The process of claim 9 wherein the vinyl monomer is selected from the group consisting of styrene, vinylnaphthalene, vinylpyridine, vinylpyrrolidone, vinylcarbazole, methylstyrenes, metilcloroestireno, p-tert-butylstyrene, methylvinylpyridine, etilvinilpiridina, acrylonitrile, methacrylonitrile, esters of acrylic acid, esters of methacrylic acid, and mixtures thereof.
11. 11. The process of claim 10, wherein the vinyl monomer is selected from the group consisting of styrene, acrylonitrile, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, methyl acrylate, butyl methacrylate, and mixtures thereof.
12. 12. The process of claim 11, wherein the vinyl monomer is selected from the group consisting of styrene, methyl methacrylate, and mixtures thereof. The process of claim 1, wherein the primary reducing agent is ferrous sulfate and the chelating agent is triethylene tetramine.